Push-to-talk (abbreviated as PTT or P2T) is a two-way communication method that uses half-duplex mode where transmission occurs in both directions, but not at the same time.
To use PTT, users must press a button on the PTT device while speaking, then release it when done. The listener must then do the same to respond. Common PTT devices include the walkie-talkie. Newer PTT systems use VoIP to provide digital PTT service over 3G data networks. Synonymous with press-to-talk.
PTT PoC or Push to Talk over Cellular is a service option for a cellular phone network which permits subscribers to use their phone as a walkie-talkie. A typical Push to Talk connection connects almost instantly. One significant advantage of PoC is that it allows a single person to reach an active talk group with a single button press; users no longer need to make several calls to coordinate with a group.
Push-to-talk cellular calls are half duplex communications — while one person transmits, the other(s) receive. Traditional mobile phone networks and devices utilize full-duplex communications, allowing customers to call other persons on a mobile or land-line network and be able to simultaneously talk and hear the other party.
Such communications require a connection to be started by dialing a phone number and the other party answering the call, and the connection remains active until either party ends the call or the connection is dropped due to signal loss or a network outage.
Therefore, telephone communication protocol does not allow for casual and immediate transmissions to be sent to other parties on the network. Whereas telephone calls require the lengthy process of dialing, network switching and routing, call setup, and waiting for the other party to answer, a two-way radio has a much quicker protocol because of the immediacy of push to talk communication.
Full-duplex operation on mobile phone networks is made possible by using separate frequencies for transmission and reception. Mobile Push-to-Talk service, offered by some mobile carriers, adds functionality for individual half-duplex transmissions to be sent to another party on the system without needing an existing connection to be already established.
Since the system is half-duplex, only one user can transmit by PTT at a time; the other party is unable to transmit until the transmitting user unkeys their PTT button. Currently, PTT service is supported only between parties on the same mobile carrier service, and users with different carriers will be unable to transmit to each other by PTT.
In addition to mobile handsets, the Push-to-Talk service might be complemented with fixed PC applications acting as PTT clients connected to the mobile operator via secured Internet links. A specialized type of PC Client is a dispatcher, similar to a PC client but designed for heavy load dispatching.
That is, coordinating many issues typically caused when managing large fleets from a dispatch center. In Spain, Telefonica has launched PTT offering with focus on dispatch orientated group communications.
When used with GSM and CDMA networks, the PTT service commonly does not use up the regular airtime minutes that are available for general voice calls.
Thursday, January 21, 2010
Saturday, January 16, 2010
Blu-Ray > New Era in Compact World
Blu-ray (not Blue-ray) also known as Blu-ray Disc (BD), is the name of a next-generation optical disc format jointly developed by the Blu-ray Disc Association (BDA), a group of the world's leading consumer electronics, personal computer and media manufacturers (including Apple, Dell, Hitachi, HP, JVC, LG, Mitsubishi, Panasonic, Pioneer, Philips, Samsung, Sharp, Sony, TDK and Thomson).
The format was developed to enable recording, rewriting and playback of high-definition video (HD), as well as storing large amounts of data.
The format offers more than five times the storage capacity of traditional DVDs and can hold up to 25GB on a single-layer disc and 50GB on a dual-layer disc. This extra capacity combined with the use of advanced video and audio codecs will offer consumers an unprecedented HD experience.
While current optical disc technologies such as DVD, DVD±R, DVD±RW, and DVD-RAM rely on a red laser to read and write data, the new format uses a blue-violet laser instead, hence the name Blu-ray.
Despite the different type of lasers used, Blu-ray products can easily be made backwards compatible with CDs and DVDs through the use of a BD/DVD/CD compatible optical pickup unit. The benefit of using a blue-violet laser (405nm) is that it has a shorter wavelength than a red laser (650nm), which makes it possible to focus the laser spot with even greater precision.
This allows data to be packed more tightly and stored in less space, so it's possible to fit more data on the disc even though it's the same size as a CD/DVD. This together with the change of numerical aperture to 0.85 is what enables Blu-ray Discs to hold 25GB/50GB. Recent development by Pioneer has pushed the storage capacity to 500GB on a single disc by using 20 layers.
Blu-ray is currently supported by about 200 of the world's leading consumer electronics, personal computer, recording media, video game and music companies. The format also has support from all Hollywood studios and countless smaller studios as a successor to today's DVD format. Many studios have also announced that they will begin releasing new feature films on Blu-ray Disc day-and-date with DVD, as well as a continuous slate of catalog titles every month. For more information about Blu-ray movies, check out our Blu-ray movies and Blu-ray reviews section which offers information about new and upcoming Blu-ray releases, as well as what movies are currently available in the Blu-ray format.
The format was developed to enable recording, rewriting and playback of high-definition video (HD), as well as storing large amounts of data.
The format offers more than five times the storage capacity of traditional DVDs and can hold up to 25GB on a single-layer disc and 50GB on a dual-layer disc. This extra capacity combined with the use of advanced video and audio codecs will offer consumers an unprecedented HD experience.
While current optical disc technologies such as DVD, DVD±R, DVD±RW, and DVD-RAM rely on a red laser to read and write data, the new format uses a blue-violet laser instead, hence the name Blu-ray.
Despite the different type of lasers used, Blu-ray products can easily be made backwards compatible with CDs and DVDs through the use of a BD/DVD/CD compatible optical pickup unit. The benefit of using a blue-violet laser (405nm) is that it has a shorter wavelength than a red laser (650nm), which makes it possible to focus the laser spot with even greater precision.
This allows data to be packed more tightly and stored in less space, so it's possible to fit more data on the disc even though it's the same size as a CD/DVD. This together with the change of numerical aperture to 0.85 is what enables Blu-ray Discs to hold 25GB/50GB. Recent development by Pioneer has pushed the storage capacity to 500GB on a single disc by using 20 layers.
Blu-ray is currently supported by about 200 of the world's leading consumer electronics, personal computer, recording media, video game and music companies. The format also has support from all Hollywood studios and countless smaller studios as a successor to today's DVD format. Many studios have also announced that they will begin releasing new feature films on Blu-ray Disc day-and-date with DVD, as well as a continuous slate of catalog titles every month. For more information about Blu-ray movies, check out our Blu-ray movies and Blu-ray reviews section which offers information about new and upcoming Blu-ray releases, as well as what movies are currently available in the Blu-ray format.
Emerging EDGE now
EDGE (Enhanced Data rate for GSM Evolution) is a specification for data transfer on GSM networks.
EDGE/EGPRS is implemented as a bolt-on enhancement for 2G and 2.5G GSM and GPRS networks, making it easier for existing GSM carriers to upgrade to it. EDGE/EGPRS is a superset to GPRS and can function on any network with GPRS deployed on it, provided the carrier implements the necessary upgrade.
EDGE requires no hardware or software changes to be made in Global System for Mobile Communications core networks. EDGE compatible transceiver units must be installed and the base station subsystem needs to be upgraded to support EDGE. If the operator already has this in place, which is often the case today, the network can be upgraded to EDGE by activating an optional software feature. Today EDGE is supported all major chip vendors for both GSM and WCDMA/HSPA.
EDGE features both a packet capability, EGPRS (Enhanced General Packet Radio Service), and a circuit switched capability, ESCD (Enhanced Circuit Switched Data).
EDGE packs up to 69.2Kbps into eight timeslots, for a total theoretical bandwidth of 473.6Kb.
GERAN (GSM/EDGE Radio Access Network) is the name given to the 3GPP standards for GSM/EDGE radio access.
EDGE is an update to GPRS. In turn, EDGE will eventually be replaced by WCDMA (Wideband Code Division Multiple Access)
EDGE/EGPRS is implemented as a bolt-on enhancement for 2G and 2.5G GSM and GPRS networks, making it easier for existing GSM carriers to upgrade to it. EDGE/EGPRS is a superset to GPRS and can function on any network with GPRS deployed on it, provided the carrier implements the necessary upgrade.
EDGE requires no hardware or software changes to be made in Global System for Mobile Communications core networks. EDGE compatible transceiver units must be installed and the base station subsystem needs to be upgraded to support EDGE. If the operator already has this in place, which is often the case today, the network can be upgraded to EDGE by activating an optional software feature. Today EDGE is supported all major chip vendors for both GSM and WCDMA/HSPA.
EDGE features both a packet capability, EGPRS (Enhanced General Packet Radio Service), and a circuit switched capability, ESCD (Enhanced Circuit Switched Data).
EDGE packs up to 69.2Kbps into eight timeslots, for a total theoretical bandwidth of 473.6Kb.
GERAN (GSM/EDGE Radio Access Network) is the name given to the 3GPP standards for GSM/EDGE radio access.
EDGE is an update to GPRS. In turn, EDGE will eventually be replaced by WCDMA (Wideband Code Division Multiple Access)
Monday, January 11, 2010
HDMI (High-Definition Multimedia Interface)
HDMI (High-Definition Multimedia Interface)is a compact audio/video interface for transmitting uncompressed digital data.
It represents a digital alternative to consumer analog standards, such as radio frequency (RF) coaxial cable, composite video, S-Video, SCART, component video, D-Terminal, or VGA. HDMI connects digital audio/video sources—such as set-top boxes, Blu-ray Disc players, personal computers (PCs), video game consoles
HDMI supports, on a single cable, any TV or PC video format, including standard, enhanced, and high-definition video; up to 8 channels of digital audio;
HDMI (High-Definition Multimedia Interface) is the first and only industry-supported, uncompressed, all-digital audio/video interface. By delivering crystal-clear, all-digital audio and video via a single cable, HDMI dramatically simplifies cabling and helps provide consumers with the highest-quality home theater experience. HDMI provides an interface between any audio/video source, such as a set-top box, DVD player, or A/V receiver and an audio and/or video monitor, such as a digital television (DTV), over a single cable.
HDMI supports standard, enhanced, or high-definition video, plus multi-channel digital audio on a single cable. It transmits all ATSC HDTV standards and supports 8-channel, 192kHz, uncompressed digital audio and all currently-available compressed formats (such as Dolby Digital and DTS), HDMI 1.3 adds additional support for new lossless digital audio formats Dolby® TrueHD and DTS-HD Master Audio™ with bandwidth to spare to accommodate future enhancements and requirements.
• HDMI is the de facto standard digital interface for HD and the consumer electronics market: More than 700 companies have become adopters, and nearly 200 million devices featuring HDMI are expected to ship in 2008, with an installed based of nearly one billion HDMI devices by 2010 (conservative estimates by In-Stat).
• Convergence – HDMI is the interface for convergence of PC and consumer electronics devices: HDMI enables PCs to deliver premium media content including high definition movies and multi-channel audio formats. HDMI is the only interface enabling connections to both HDTVs and digital PC monitors implementing the DVI and HDMI standards.
• Evolving standard – HDMI is continually evolving to meet the needs of the market: Products implementing new versions of the HDMI specification will continue to be fully backward compatible with earlier HDMI products
It represents a digital alternative to consumer analog standards, such as radio frequency (RF) coaxial cable, composite video, S-Video, SCART, component video, D-Terminal, or VGA. HDMI connects digital audio/video sources—such as set-top boxes, Blu-ray Disc players, personal computers (PCs), video game consoles
HDMI supports, on a single cable, any TV or PC video format, including standard, enhanced, and high-definition video; up to 8 channels of digital audio;
HDMI (High-Definition Multimedia Interface) is the first and only industry-supported, uncompressed, all-digital audio/video interface. By delivering crystal-clear, all-digital audio and video via a single cable, HDMI dramatically simplifies cabling and helps provide consumers with the highest-quality home theater experience. HDMI provides an interface between any audio/video source, such as a set-top box, DVD player, or A/V receiver and an audio and/or video monitor, such as a digital television (DTV), over a single cable.
HDMI supports standard, enhanced, or high-definition video, plus multi-channel digital audio on a single cable. It transmits all ATSC HDTV standards and supports 8-channel, 192kHz, uncompressed digital audio and all currently-available compressed formats (such as Dolby Digital and DTS), HDMI 1.3 adds additional support for new lossless digital audio formats Dolby® TrueHD and DTS-HD Master Audio™ with bandwidth to spare to accommodate future enhancements and requirements.
• HDMI is the de facto standard digital interface for HD and the consumer electronics market: More than 700 companies have become adopters, and nearly 200 million devices featuring HDMI are expected to ship in 2008, with an installed based of nearly one billion HDMI devices by 2010 (conservative estimates by In-Stat).
• Convergence – HDMI is the interface for convergence of PC and consumer electronics devices: HDMI enables PCs to deliver premium media content including high definition movies and multi-channel audio formats. HDMI is the only interface enabling connections to both HDTVs and digital PC monitors implementing the DVI and HDMI standards.
• Evolving standard – HDMI is continually evolving to meet the needs of the market: Products implementing new versions of the HDMI specification will continue to be fully backward compatible with earlier HDMI products
Friday, January 8, 2010
Android OS on Mobile
Android is the name of the Mobile Operating system owned by Google now.
As we all know, today the mobile phone applications have been developed by Java libraries.
It allows developers to write managed code in the Java language, controlling the device via Google-developed Java libraries.
The first phone to run the Android operating system was the HTC Dream, released on 22 October 2008
By the end of 2009 there will be at least 18 phone models using Android worldwide, according to Google. In addition to the mobile devices that ship with Android, some users have been able (with some amount of hacking, and with limited functionality) to install it on mobile devices shipped with other operating systems.
As we all know, today the mobile phone applications have been developed by Java libraries.
It allows developers to write managed code in the Java language, controlling the device via Google-developed Java libraries.
The first phone to run the Android operating system was the HTC Dream, released on 22 October 2008
By the end of 2009 there will be at least 18 phone models using Android worldwide, according to Google. In addition to the mobile devices that ship with Android, some users have been able (with some amount of hacking, and with limited functionality) to install it on mobile devices shipped with other operating systems.
GPS and Compass @ Digital Camera
Is it possible to have a GPS & Compass in a compact digital camera.
Yes. It has done by Sony.
Sony has designed two new innovative Cyber-shot cameras (models DSC-HX5V and DSC-TX7) that are the world’s first compact digital still cameras to include full HD (1920 x 1080 60i) Advanced Video Codec High Definition (AVCHD) video capability. They are also the world’s smallest and thinnest AVCHD capable cameras.
According to the announcement, these are the first Cyber-shot cameras with an in-camera Backlight Correction High Dynamic Range (HDR) feature for managing difficult lighting situations and TransferJet™ wireless technology for sharing, storing and viewing images. The HX5V model is also the world’s first still camera to include GPS + Compass and Optical SteadyShot™ with Active Mode technologies. Ideal for travelers who take hundreds of photos, the in-camera GPS + Compass feature on the HX5V camera makes it easy to store and share the location and direction of where photos were taken
Yes. It has done by Sony.
Sony has designed two new innovative Cyber-shot cameras (models DSC-HX5V and DSC-TX7) that are the world’s first compact digital still cameras to include full HD (1920 x 1080 60i) Advanced Video Codec High Definition (AVCHD) video capability. They are also the world’s smallest and thinnest AVCHD capable cameras.
According to the announcement, these are the first Cyber-shot cameras with an in-camera Backlight Correction High Dynamic Range (HDR) feature for managing difficult lighting situations and TransferJet™ wireless technology for sharing, storing and viewing images. The HX5V model is also the world’s first still camera to include GPS + Compass and Optical SteadyShot™ with Active Mode technologies. Ideal for travelers who take hundreds of photos, the in-camera GPS + Compass feature on the HX5V camera makes it easy to store and share the location and direction of where photos were taken
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